Digital broadband broadcast networks enable end users to receive digital content including video, audio, data, and so forth. Using a mobile terminal, a user may receive digital content over a wireless digital broadcast network.
The capacity of a wireless transmission channel, e.g., in a digital broadcasting system, can be divided between different services by using time-division multiplexing (TDM). In such a situation, each service reserves one slot from a TDM frame resulting in a fixed bit rate. The bit rate is determined by the size of the slot and the frame interval. Some services can have a variable bit rate. One example of such services is a real-time video service.
An issue arises because the TDM capacity should be reserved according to the maximum bit rate of the video service to guarantee that the stream will fit into the reserved slot. However, most of the time the reserved slots and/or the transmission frames are not completely filled resulting in wasted transmission capacity. FIG. 1 shows an example unused transmission capacity in a TDM slot and frame structure. In the example of FIG. 1, four different real time services are represented, and each service reserves one time slot per frame. As shown in FIG. 1, data fills less than the entirety of each slot, which results in unused capacity.
A potential solution to the unused capacity issue is to use the unused capacity from the real time services for one ore more non-real time services, such as, a file carousel. However, this leads to another problem.
Typically, broadcasting networks have a signaling method that indicates to receivers when the services, either real time or non-real time, are being broadcast (i.e., are “on the air”). One example of such signaling is the Electronic Service Guide (ESG) in IP Datacast (IPDC) over DVB-H network. FIG. 2 is a schematic diagram of an example IPDC over DVB-H system where services include real time video services and non-real time services in a file carousel. In this case, the non-real time services reserve a fixed bit rate and do not use the unused capacity. This makes it possible to use an ESG to send start and end times of the files.
In a file carousel, where files are sent repeatedly on the same channel, the start and end times for each file can be calculated from the constant bit rate of the channel and the sizes of the files. These start and end times are then signaled in the ESG such that the receiver does not have to stay on all the time, but can save power and switch on just before the desired file is transmitted.
Another issue arises when the unused capacity from the real time services is utilized in a file carousel. That is, it is impossible to calculate when a particular file is on the air. This is caused by the fact that the bit rate is no longer constant, but changes in an unpredictable (random) manner.
More efficient ways of digitally broadcasting best-effort services would advance the art.